Coring apparatus

ABSTRACT

A formation coring apparatus suitable for coring relatively soft formations which apparatus includes a core barrel with an interior surface having properties similar to synthetic rubber and two semitubular rigid portions joined along at least one of the adjacent edges by a flexible material, a core catcher having a plurality of flexible segments adapted to open while the core is being drilled and to close with the segments supporting the core thereabove to recover the core, a coring bit and a wire line tool adapted to carry the core barrel and the core catcher into position within the coring bit and having a fishing neck to be engaged by a wire line device for recovery, a latch for retaining the tool in position within the coring bit, a swivel allowing the core barrel and catcher to remain stationary while the coring bit is rotated and a check valve allowing fluid flow from the top of the core barrel because of the entry of the core therein to flow out the tool while preventing inflow of fluids into the top of the tool.

Young et al.

3,874,465 Apr. 1, 1975 [54] CORING APPARATUS FOREIGN PATENTS OR APPLICATIONS 1 1 Inventors/1 J01l1 Wallace Young; Robert 201,134 H1966 Sweden 175/249 Charles F irkins, both of Flatonia; 52 29 Primary Examiner-David H. Brown 0 0 Gus a 0 Attorney, Agent, or FirmJack R. Springgate; Joe E. [73] Assignee: The Randolph Company, Houston, Edwards; M. H. Gay

Tex.

[22] Filed: Oct. 2, 1973 [57] ABSTRACT [21] Appl, No.; 402,920 A formation coring apparatus suitable for coring relatively soft formations which apparatus includes a core barrel with an interior surface having properties simi- [52] US. Cl 175/236, 175/239, 117755/224531, lar to Synthetic rubber and two semitubular rigid Pop 51 I Cl Ezlb 00 tions joined along at least one of the adjacent edges by 1 'E 232 a flexible material, a core catcher having a plurality of [58] g flexible segments adapted to open while the core is l being drilled and to close with the segments supporting the core thereabove to recover the core, a coring bit and a wire line tool adapted to carry the core bar- [56] References cued rel and the core catcher into position within the coring UNITED STATES PATENTS bit and having a fishing neck to be engaged by a wire 2,083,062 6/1937 Hampton 175/240 X line device for recovery, a latch for retaining the tool 2,189,057 2/1940 Copelin 175/236 X in position within the coring bit, a swivel allowing the Catland et a1. core barrel and catcher to remain tationary the 2,315,590 4/1943 Cantrell 174/340 coring bi i rotated and a check valve allowing fluid glldlebmndt flow from the top of the core barrel because of the 310398l 9/1963 y entry of the core therein to flow out the tool while arper 175/236 fl ffl 1 3,180,438 4/1965 Dickinson et a1 175/239 Preventmg 0W 0 S the t0P Ofthe 3,285,354 11/1966 Sanders et al. 175/242 3,409,094 11/1968 Kretschmer et al. 175/254 x 15 6 Drawmg F'gures 7 I 7 lI-IIl I In 1 [I e M ti; "F ia FATEHTED APR 1 5 SHEET 1 BF 2 CORING APPARATUS The coring of well formations has long been used as a method of recovering a sample of the actual formation which has not been broken up by the drilling action of the drill bit. There have been prior devices which could be operated or recovered by wire line which devices were used to recover formation samples. The advantages of the utilization of the wire line device is very substantial since its recovery is much simpler and quicker than the pulling of an entire drill string. This advantage is even more pronounced in deep wells.

To date none of the available coring apparatus is completely acceptable for coring a soft relatively friable formation such as unconsolidated sands making up a column of sediments that would not maintain its structural integrity under its own weight. Efforts have been made to provide suitable coring for such soft for- SUMMARY The present invention provides an improved coring apparatus which is suitable for coring soft formations.

An object of the present invention is to provide an improved formation coring apparatus which will retain and protect a core cut from a soft formation.

Another object is to provide an improved formation coring apparatus which is suitable for coring soft formations and which is of simple construction and simple and easy to use.

A further object is to provide an improved formation coring device for wire line coring.

Another object is to provide an improved formation coring apparatus which can recover a complete core even in soft formation.

Still another object is to provide an improved formation coring apparatus which minimizes washing of the core during coring by the drilling fluids.

A still further object is to provide an improved combination of apparatus including a coring bit which assures that the core entrance is not blocked.

Another object is to provide an improved core barrel and core catcher apparatus for a formation coring apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantages of the present invention are hereinafter set forth and explained with reference to the structures illustrated in the drawings wherein:

FIGS. 1A and 1B are longitudinal sectional views of the improved coring apparatus of the present invention with FIG. 18 being the lower extension of FIG. 1A.

FIG. 2 is a transverse sectional view of one form of the improved core barrel of the present invention.

FIG. 3 is a transverse sectional view of another form of the improved core barrel of the present invention.

FIG. 4 is an upper end view of the improved corecatcher of the present invention.

FIG. 5 is a sectional view of the core catcher taken along line 5-5 in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The improved apparatus illustrated in FIGS. 1A and 1B includes the drill string 10 with the coring bit 12 on the lower end thereof and the wire line tool 14 positioned therein as shown. The upper end of drill string 10 is not shown for purpose of clarity. The ring 16 is positioned by threading into the female threads 18 of the drill string section to provide a downward facing shoulder for latching the wire line tool 14 within the drill string 10 as hereinafter described.

The coring bit 12 is annular in shape and defines the internal annular seat 20 which is curved in shape to allow wire line tool 14 to properly seat therein when it enters the coring bit 12. To assist in this seating the exterior of the lower end of the wire line tool 14 has a complementary shape to the shape of the seat 20. The wire line tool 14 includes the tubular housing 22 and the bull nose 24 at its lower end which has the exterior shape to mate with seat 20.

The upper end of wire line tool 14 includes the fishing neck 26 which allows the tool 14 to be dropped through the drill string 10 and, when a core is ready for recovery, the neck 26 of tool 14 is engaged by a standard wire line device to allow the tool 14 to be raised through the drill string 10. Immediately below the top of tool 14 is the latch 28 which engages under ring 16 as shown to retain the tool 14 in its seated position within the drill string 10 and the coring bit 12.

Since the core is cut in the formation by rotating the drill string 10 and coring bit 12, it is desired that the core be protected from rotation of the core barrel 30 and the core catcher 32 which are positioned within tool 14. The tool 14 has the swiveljoint 34 mounted between the latch 28 and the housing 22. Swivel joint 34 is of standard construction and allows the upper end of tool 14 to rotate with drill string 10 because of the engagement of latch 28 with ring 16 and the lower end or housing portion of tool 14 can remain motionless with respect to the core which is cut by the coring bit.

Another feature of the wire line tool 14 is that it includes the check valve 36, which check valve allows flow outwardly from the upper portion of the housing 22 but also prevents inflow of fluids into the top of the housing 22. The inclusion of check valve 36 in the wire line tool 14 prevents the erosion of the core which would be caused by the displacement of fluids when the core enters the core barrel. This is accomplished by allowing the fluids within the core barrel 30 to be displaced from the upper portion of the housing 22 so that such displaced fluids are not circulated out through the bottom of the core barrel and core catcher during the cutting of the core. In soft formations the flow of drilling fluids being displaced by the core in the core barrel 30 over the exterior of the core would cause erosion of the core to thereby effectively prevent the recovery of a truly representative sample of the formation being cored.

In the coring of soft formations it has been found desirable that the core barrel have an interior surface which will support the core within the barrel without causing abrasion of the core on the inner surface of the barrel as it is being formed and moves into the core barrel. The core barrel 30 of the present invention has been found to be a great improvement over prior core barrels in that it does provide the interior surface having sufficient friction to support the core therein but does not damage the core as it is being formed.

In the form of core barrel illustrated in FIG. 2 there is shown a composite structure in which a pair of opposed semitubular members 38 which extend longitudinally over the length of the core barrel 30 are molded integrally with the lining 40 to provide a hollow tubular structure of the core barrel. The semitubular members 38 may be of suitable metal such as a cold drawn steel tubing material ASME I015 or an ASME 5052 aluminum alloy which gives the semitubular members sufficient rigidity to provide the core barrel with structural integrity. Also if desired the semitubular members may be made of an epoxy material reinforced with fiberglass. The lining 40 is preferred to be of a synthetic rubber material such as the B. F. Goodrich Hycar Buna N or the Dupont Neoprene or a natural rubber all of which are preferred to have a hardness of approximately 70 durometer on the Shore A scale. Such materials provide a sufficient flexibility of the core barrel to prevent damage to the exterior of the core as it slides into the barrel. Also it is noted that when the core is recovered the lining 40 may be cut along a line between one pair of the opposed or adjacent edges of the semitubular members 38 and the core barrel 30 opened up to completely expose the core therein. This allows the core to be delivered to the core analysis site with minimum displacement. Once the core barrel 30 has been cut as described above, it can be reused and will function properly since the lining 40 is of sufficient strength resilience and flexibility to cause the core barrel to assume its normal shape and further it will be supported by the housing 22 of the wire line tool 14.

The modified form of core barrel illustrated in FIG. 3 is an extruded tube which may be of a polypropylene material. It is noted that this core barrel 42 is provided with two semitubular sections 44 joined by reduced sections 46 extending axially along the length of the core barrel. The core barrel 42 functions in the same manner as the core barrel illustrated in FIG. 2 in that the reduced sections 46 have greatly reduced thickness to provide an area of flexibility and resilience about which the core barrel may be pivoted when one of these sections is severed to allow the core to be removed. As in the case with the previously described core barrel 30, core barrel 42 can be reused even after it has been severed along one side.

The core catcher 32 which is adapted to be positioned within the bull nose 24 and to rest on the internal shoulder 48 of bull nose includes an outer cylindrical ring 50, the annular lining 52 and the means for retaining the core within the core barrel as it is being removed. The improved core catcher of the present invention includes as such retaining means a plurality of leaves or segments 54 which in their normally closed position as shown in the drawings extend upwardly at a substantial angle and intersect with each other to form a closure blocking of the central opening through the catcher 32. Each of the segments 54 includes a reinforcing rib 56 which is made integral with the segment and also with the annular lining 52. With the ribs 56 positioned above the segments 54 and being sufficiently flexible. such ribs 56 do not interfere with the opening of the segments 54 to allow the core being cut to enter the core barrel 30 through the core catcher 32. However, when it is desired to have the core catcher 32 retain the core within the core barrel 30, the segments 54 also being resilient, return to their closed position as shown in FIG. 5. The reinforcing ribs 56 and the archlike engagement of the segments 54 with each other by virtue of their upward inclination provide a very substantial retention of the core within the core barrel by the core catcher 32.

In operation with the core bit 12 and drill string 10 positioned in the bore hole and ready to commence coring. the wire line tool 14 is first loaded with the core barrel 30 being inserted into the interior of the housing 22 and the core catcher 32 is positioned within the bull nose 24. The bull nose 24 is then threaded on to the housing 22. With the core catcher 32 positioned on the shoulder 48 within the bull nose 24 the core catcher provides a support for the core barrel 30 to maintain it within the housing.

To position the wire line tool 14 within the drill string 10 and coring bit 12 it is merely allowed to fall through the drill string which is completely filled with drilling fluid. The drilling fluid slows the descent of the tool to prevent its damage. In the event the coring is done with air it is recommended that the tool 14 be lowered on a wire line into its position within the drill string 10 and the coring bit 12 to prevent damage.

With the tool 14 in position the drill string 10 is rotated to commence cutting the core and as the drill string 10 is lowered the core enters the central opening of the drill bit 12, passes upwardly through the core catcher 32 by flexing of the segments 54 upwardly and outwardly and enters the core barrel 30. On completion ofa core of a particular length, the rotation of the drill string is stopped and a wire line fishing device is lowered into engagement with the fishing neck 26 of the tool 14. The tool 14 is then removed from the drill string 10 by raising a wire line. At the surface the bull nose 24 with the core catcher 32 therein is removed from the housing 22. This leaves the core barrel 30 exposed and it is removed and kept so that the core may be preserved as intact as possible for its examination. The tool 14 may be rerun by inserting a new core barrel 30 therein and closing the lower end thereof by threading the bull nose 24 with the core catcher 32 therein onto the lower end of the housing 22. Again the tool 14 is dropped in place or otherwise lowered into the drill string 10. The exterior configuration ofthe bull nose 24 is such that it coacts with the seat 20 to assure that the tool 14 is substantially centered with respect to the central opening of the coring bit 12.

It is recommended that the clearance between the outside diameter of the bull nose 24 and the inside diameter of the coring bit seat 20 be as close as possible and. if desired, seals may be used. Also it is suggested that the combined length of the opening through the coring bit 12 and the bull nose 24 be between A: and l /2 inch. It has been found that greater lengths in certain formations can cause a clogging of the openings of this opening. Further, it should be noted that the coring bit 12 is provided with the downward projection 58 immediately surrounding its central opening. Such projection is desirable since it prevents washing out of well fluids and thus avoids damage to the core.

Further it is recommended that the drilling fluids holes 60 be positioned with respect to the center of the bit face to be as far from the center as possible and still provide adequate lubrication. It has been found that in some cases the fluid holes 60 may be on the side of the bit as shown in FIG. 1B.

From the foregoing it can be seen that the improved coring apparatus of the present invention is easily used as a wire line operation and provides for the bleeding of drilling fluids from the core barrel to assure that the core is not washed overly as the drilling fluid is displaced by the core within the core barrel. Further, the improved core catcher provides adequate support for the core while providing only a minimum of resistance to the passing of the core therethrough. Also in the design of the coring apparatus of the present invention every effort is made to minimize the clearances so that there is a minimum of washing ofthe drilling fluids over the core as it is formed.

What is claimed is:

1. A formation coring apparatus. comprising a tubular member having rigid semitubular members joined along at least one of their adjacent edges by a resilient. flexible material.

said semitubular members being of a material on their inner surface suitable for supporting a loose core from a soft formation without damaging such core.

2. A formation coring apparatus according to claim 1, including a catcher located beneath the lower extremity of said tubular member and being generally tubular in shape and having resilient core retaining means adapted to normally span the bore of said catcher.

3. A formation coring apparatus according to claim 1, wherein said semitubular members are metal.

4. A formation coring apparatus according to claim 1, wherein said semitubular members are a rigid plastic material.

5. A formation coring apparatus according to claim 1 wherein said tubular member is an extruded tube having axially extending. opposed sections of reduced thickness.

said tubular member being of a material suitable as a lining for supporting a loose core without damage thereto.

6. A formation coring apparatus. comprising a core barrel having two semitubular members having their edges extending axially in close spaced relationship.

means resiliently connecting at least one pair of adjacent edges of said semitubular members.

means lining said core barrel to receive a core from a soft formation therein without damage thereto. a core catcher having a tubular body and resilient closure means adapted to open freely to admit a core from a soft formation therein from one direction and resiliently close to prevent a core from passing therethrough in the other direction.

means for supporting said core barrel and said core catcher in aligned position.

said supporting means including a tubular housing and a bull nose.

a coring bit having a central bore,

said supporting means adapted to be positioned within the central bore of said coring bit with said core catcher positioned within the lower portion of said central bit bore and said core barrel positioned on and extending above said core catcher whereby a core cut by said coring bit enters through said core catcher into said core barrel.

7. A formation coring apparatus according to claim 6, wherein the clearance between said supporting means and the lower interior of said bit is minimized.

8. A formation coring apparatus according to claim 6, wherein the internal length of the core diameter portion of said bull nose and said coring bit is less than l /2 inches.

9. A formation coring apparatus according to claim 6, including means connected to said supporting means for engagement by a wire line.

10. A formation coring apparatus according to claim 9 wherein said wire line engaging means includes a housing, and

a latch within said housing and adapted to engage below a shoulder within said coring bit to retain said supporting means therein.

11. A formation coring apparatus according to claim 9 wherein said wire line engaging means includes a housing and.

a check valve allowing flow upwardly out of said housing and said supporting means and preventing downward flow wherein.

12. A formation coring apparatus according to claim 9 wherein said wire line engaging means includes a housing. and

a swivel connecting said housing to said supporting means so that as said housing rotates with said coring bit, said core barrel and said core catcher may receive a core without a rotary motion.

13. In a formation coring apparatus having a core barrel. a core catcher comprising a tubular housing having a central bore,

a plurality of flexible segments mounted in said housing.

said segments being normally positioned to close the central core through said housing. and

means coacting with said segments to restrain their movement in one direction to retain a core within the core barrel while allowing freedom of movement of the segments in the other direction so that a core being cut from a soft formation will flex the segments upwardly and outwardly to permit entry of the core into the core barrel without damage to the core.

14. In a coring apparatus a core catcher according to claim 13, wherein said segments in closed position form a cone having an apex pointing in the direction of free opening of said segments.

15. In a coring apparatus, a core catcher according to claim 14, including resilient ribs secured to said tubular housing and to the upper side of the cone of said segments with at least one of said ribs secured to each of said segments whereby said ribs provide said restraining 

1. A formation coring apparatus, comprising a tubular member having rigid semitubular members joined along at least one of their adjacent edges by a resilient, flexible material, said semitubular members being of a material on their inner surface suitable for supporting a loose core from a soft formation without damaging such core.
 2. A formation coring apparatus according to claim 1, including a catcher located beneath the lower extremity of said tubular member and being generally tubular in shape and having resilient core retaining means adapted to normally span the bore of said catcher.
 3. A formation coring apparatus according to claim 1, wherein said semitubular members are metal.
 4. A formation coring apparatus according to claim 1, wherein said semitubular members are a rigid plastic material.
 5. A formation coring apparatus according to claim 1 wherein said tubular member is an extruded tube having axially extending, opposed sections of reduced thickness, said tubular member being of a material suitable as a lining for supporting a loose core without damage thereto.
 6. A formation coring apparatus, comprising a core barrel having two semitubular members having their edges extending axially in close spaced relationship, means resiliently connecting at least one pair of adjacent edges of said semitubular members, means lining said core barrel to receive a core from a soft formation therein without damage thereto, a core catcher having a tubular body and resilient closure means adapted to open freely to admit a core from a soft formation therein from one direction and resiliently close to prevent a core from passing therethrough in the other direction, means for supporting said core barrel and said core catcher in aligned position, said supporting means including a tubular housing and a bull nose, a coring bit having a central bore, said supporting means adapted to be positioned within the central bore of said coring bit with said core catcher positioned within the lower portion of said central bit bore and said core barrel positioned on and extending above said core catcher whereby a core cut by said coring bit enters through said core catcher into said core barrel.
 7. A formation coring apparatus according to claim 6, wherein the clearance between said supporting means and the lower interior of said bit is minimized.
 8. A formation coring apparatus according to claim 6, wherein the internal length of the core diameter portion of said bull nose and said coring bit is less than 1 1/2 inches.
 9. A formation coring apparatus according to claim 6, including means connected to said supporting means for engagement by a wire line.
 10. A formation coring apparatus according to claim 9 wherein said wire line engaging means includes a housing, and a latch within said housing and adapted to engage below a shoulder within said coring bit to retain said supporting means therein.
 11. A formation coring apparatus according to claim 9 wherein said wire line engaging means includes a housing and, a check valve allowing flow upwardly out of said housing and said supporting means and preventing downward flow wherein.
 12. A formation coring apparatus according to claim 9 wherein said wire line engaging means includes a housing, and a swivel connecting said housing to said supporting means so that as said housing rotates with said coring bit, said core barrel and said core catcher may receive a core without a rotarY motion.
 13. In a formation coring apparatus having a core barrel, a core catcher comprising a tubular housing having a central bore, a plurality of flexible segments mounted in said housing, said segments being normally positioned to close the central core through said housing, and means coacting with said segments to restrain their movement in one direction to retain a core within the core barrel while allowing freedom of movement of the segments in the other direction so that a core being cut from a soft formation will flex the segments upwardly and outwardly to permit entry of the core into the core barrel without damage to the core.
 14. In a coring apparatus a core catcher according to claim 13, wherein said segments in closed position form a cone having an apex pointing in the direction of free opening of said segments.
 15. In a coring apparatus, a core catcher according to claim 14, including resilient ribs secured to said tubular housing and to the upper side of the cone of said segments with at least one of said ribs secured to each of said segments whereby said ribs provide said restraining means for said segments. 